This invention relates to a magnetic recording and/or reproduction apparatus, and more particularly to a magnetic recording and/or reproduction apparatus which includes a measuring instrument for measuring the position and the projection amount of a magnetic head.
A magnetic head employed in a magnetic recording and/or reproduction apparatus is abraded as the time of use thereof proceeds. Particularly, a magnetic head mounted on a rotary drum of the rotary head type is abraded at a higher rate and is rather shorter in life than a magnetic head of the fixed head type since the relative speed thereof to a magnetic tape is higher than that of the latter. As the abrasion of the magnetic head proceeds, also a region which forms the magnetic head gap, that is, the head depth, decreases and the contacting characteristic thereof with a magnetic tape or the electromagnetic conversion characteristics (frequency characteristics upon recording and reproduction) thereof vary significantly. Therefore, various magnetic head abrasion amount measuring methods and apparatus wherein an abrasion amount is measured from a variation of the projection amount of a magnetic head have been proposed. Also the assignee of the present invention has proposed non-contacting magnetic head abrasion amount measuring instruments which employ a magnetic device in Japanese Patent Laid-Open Applications. Nos. Heisei 7-235235, 7-353569 and 7-235249.
The non-contacting magnetic head abrasion amount measuring instruments are generally constructed such that a pair of magnetic sensors are disposed in an opposing relationship to a magnetic head held on a rotary drum at positions outside an angular range over which a magnetic head is wrapped around the rotary drum, and a variation of the gap between the magnetic head and the magnetic sensor which is caused by abrasion of the magnetic head is converted into a variation of the reluctance. In Japanese Patent Laid-Open Application No. Heisei 7-235249, it is disclosed that address data representative of the position of the magnetic head held on the rotary drum and measurement data of the projection amount corresponding to the address data are obtained based on a reference signal from a pulse generator (PG) provided on the rotary drum.
However, since the address data of the magnetic head and the corresponding measurement data of the projection amount obtained in this manner include not only measurement data of the gap between the magnetic sensor and the magnetic head but also the measurement data of the overall gap between the magnetic sensor and the outer peripheral surface of the rotary drum, the load to a central processing unit (hereinafter referred to simply as CPU) for calculating all of the measurement data is high, and a non-volatile memory of a large capacity for storing all resulting values of the calculation is required.